The present invention is directed to baby-feeding nipples, and, in particular, relates to baby-feeding nipples based on capillary action.
At present there is no baby bottle nipple on the market that even closely approximates the attributes of the human breast nipple, which delivers a continuous supply of milk without entrained air and without hard sucking until the reservoir is empty. In addition, as the baby bites on the human nipple, although it hurts the mother, the fluid flow is not completely cut off.
Commercial baby bottle nipples are made in the form of a hollow rubber shell with a feeding-tip extending from a bulbous portion, which is carried on a flexible and pliable outwardly extending flange. The types of nipples on the market differ principally in the number, size, and types of holes or slits in the feeding-tip and in the external shape that fits into the infant""s mouth. In contrast to the human nipple, there are several inherent problems associated with this design. As the baby sucks on the nipple and drains the bottle, the pressure inside the bottle is gradually reduced, resulting in a vacuum. As the baby continues to suck, the pressure will ultimately be reduced to such an extent that the nipple collapses and liquid can no longer be sucked out by the infant. At this point the infant becomes frustrated and sucks harder, frequently swallowing air, which is very undesirable since it results in colic and/or the need for burping. In addition, if the baby bites on the hollow nipple, or if particulates clog the nipple holes, the flow is totally cut off and no fluid is delivered. This also frustrates the infant. Finally, dentists have found that current nipple technology damages a baby""s bite; they recommend that babies breast feed rather than use current nipple technology.
It is obvious that there is a need to improve on the current state-of-the-art in baby feeding technology. There have been numerous attempts in the past to improve upon baby-feeding technology, in particular, nipple design. In fact, in the patent literature there are scores of patents in this area, some of which go back more than a century. To address the problem of a vacuum forming in the bottle, there have been numerous means to allow the entrance of air. One of the oldest examples, from 1901, involved the use of a concentric nipple design. Other examples involve the use of a tube or check valve in the nipple mounting flange or an air valve on the side of the bottle to let air into the bottle. An alternate approach to compensate for the vacuum is to use a collapsible plastic sac inside a baby bottle shell. In operation, the sac collapses during feeding, thus minimizing the amount of air that the baby ingests. A recent example (U.S. Pat. No. 6,053,342) involves the use of a flexible diaphragm with slits for pressure equalization.
Even with these improvements, the baby can still close off the nipple by biting, can still swallow air, and, in contrast to the human breast, the baby must suck harder to get the fluid. To alleviate this last problem and deliver fluid to the infant without hard sucking, several different versions of a nipple pump with a check valve have been proposed, for example, U.S. Pat. No. 2,960,088. These pumps are actuated by the infant biting on the nipple. Each time the infant presses down on the nipple, fluid is squirted into its mouth and each time the infant releases the nipple, the nipple is refilled.
For more than a century there have been scores of improvement patents for a baby bottle system that delivers fluid to an infant. Some of these have involved the fluid container, others have involved the nipple, and still others have involved both. To the applicants"" knowledge the only two significant improvements over the past century that are in commercial production are the collapsible sack and the elastomeric diaphragm with resealable perforations both of which help to eliminate the sucking of air by the infant. Most other approaches tend to be complex in construction, difficult and expensive to manufacture, difficult to clean and sterilize, or simply do not function as described.
Although two separate systems for dealing with the vacuum generated inside of the bottle are commercially available, it should be noted that there are still shortcomings associated with these two approaches. The thin plastic bag that collapses during feeding minimizes but does not eliminate ingestion of air and must be replaced after each feeding, because it cannot be sterilized. This, of course, results in a continuing expense beyond that of the initial expense of the bottle and nipple.
The elastomeric diaphragm with resealable perforations, being a mechanical type of check-valve, also possesses the shortcomings associated with this type of system. Like all check-valves, it is susceptible to leakage due to incomplete closure. This can result from clogging, such as particulates lodging in the slit, or from distortions in the slits. These distortions can be caused by elastomeric material changes (resulting from prolonged exposure to heat or sunlight for example) or from mechanical stresses on the edges of the slits as they open or close. In addition, like all check-valves, there is a threshold value at which each of the valves open. This threshold value, because it has to keep the valve from leaking, has to be significant and can exceed the sucking effort of a weak infant, especially after changes resulting from either time or usage. Of course, the valve will not function at this point. Additionally, if, for example, a sugar-based fluid is placed in the bottle and then allowed to dry on the diaphragm, the slit valves will not open at all until the sticky substance is removed. Finally, it should be noted that it is very difficult to clean residual fluid and bacteria from the slits when they are in their normally closed position. This can result in illness.
Clearly there is a need for a simple, inexpensive baby bottle nipple that more closely resembles the human breast nipple and its positive attributes.
Accordingly, it is an object of the present invention to provide a process for making a nursing nipple that delivers milk or water-based fluid to an infant without hard sucking by means of capillary pressure in the same way as the human breast.
Another object of the present invention is to provide a process for making a nipple with microscopic fluid pathways that cannot be closed-off when an infant bites on them and are easy to completely clean and sterilize.
Yet another object of the present invention is to provide a process for making a nipple having leak-proof hydrophobic microscopic pathways that are always open to relieve the slightest vacuum.
A further object of the present invention is to provide a process for making a nipple having an integral microscopic filter in the nipple that will keep particulates from clogging the nipple.
Other objects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
In accordance with the present invention there are provided methods for fabricating baby bottle nipples which mimic the function of the human breast nipple. In the human breast nipple, milk is delivered to the baby through 15-25 fluid-delivery capillaries called lactiferous ducts. These ducts are 2-4 centimeters in length and 500-900 microns in diameter. Baby bottle nipples fabricated in accordance with the methods of this invention have the common feature of at least one hydrophilic fluid delivery passage. In one embodiment, the fluid delivery passage is a microtube, as hereinafter described. In another embodiment, the fluid delivery passage is a microchannel, also hereinafter described. In yet another embodiment, the fluid delivery passage comprises a porous reticulated foam with interconnected pores. In each of these embodiments, the fluid delivery passage has at least one dimension in the range of 1-2000 microns. Also provided are processes for fabricating filters for separating solids from liquids.
All the nipples described in this application function on the basis of capillary pressure and thus the interior walls of the fluid-delivery passages in all the nipples in this application are made of, converted to, or coated with, a hydrophilic material that milk, water, juice, or other water-based liquids will wet. If the interior surface of the fluid-delivery passage is wet by the water-based fluid, then when there is a water-based fluid reservoir in contact with the bottle side of the nipple, the water-based fluid will be sucked into the fluid-delivery passages. That is, if the contact angle between the liquid and the capillary surface of the passage is 90xc2x0 or less, there will be no resistance to the flow of the liquid. In addition, the smaller the contact angle or the smaller the capillary passage, the greater will be the capillary force drawing the liquid into the capillary. There are two additional positive ramifications resulting from using a capillary with a hydrophilic wall for fluid-delivery. In contrast to prior art, not only will this type of capillary be extremely easy to clean and sterilize, but in addition, if the infant partially closes off the pathway by biting on the nipple, the capillary pressure will increase, providing fluid at increased pressure through the smaller opening in the feeding tip. Thus, like the human nipple, this invention provides milk at the baby""s end of the nipple without hard sucking. This means that, using the present technology, the shape of the nipple can be much closer to that of an actual human breast. In addition, these fluid-delivery passages embedded in a solid or non-reticulated porous flexible nipple body (like the human nipple) will not be easily closed off if the baby bites on the nipple. This solid or non-reticulated porous flexible nipple will therefore not adversely affect the baby""s bite as is common with hollow nipples.
In addition to the features already mentioned, the nipples described in the present application provide a means for letting air into the bottle in a continuous fashion without a pressure threshold, thereby eliminating the vacuum generated by the sucking infant. This is accomplished by placing microscopic hydrophobic passages in the form of air-admittance channels or pores in an area of the nipple which is never in the infant""s mouth. The walls of these air-admittance capillaries or pores are made of, converted to, or coated with a hydrophobic material so that air can enter the bottle, but the water-based fluid cannot flow out of the bottle if the minimum cross-sectional dimension is small enough. In the present invention, the cross-sectional dimension is usually less than 300 microns. With these small capillaries an adequate rate of air admittance is achieved by using a plurality of air-admittance capillaries.
Finally, some of the nipples described in the present application incorporate an integral microscopic filter to keep the capillaries or passages that deliver water-based fluid to the infant from clogging. The walls of the pores or channels in this microscopic filter are fabricated from or coated with a hydrophilic material. The minimum cross-sectional dimension of the pores or capillaries in the filter must be smaller that those that deliver milk or other water-based fluid to the infant so that they can effectively keep particulates that would clog the fluid-delivery pores or capillaries from entering the nipple.